Pick the situation. We'll explain what they actually have the power to do, what they don't, and what to do if they overstep. We say it both ways — including when the authority IS acting lawfully. Knowing the line is what stops the panic.
Pick the closest. Each section covers the most common UK questions about that group's powers.
Pick the closest. If your exact question isn't here, the closest match will usually still help — many of these powers overlap.